1. Field
The present disclosure relates to a method for post-treatment of a carbonaceous material using dehydrocyclization, a carbonaceous material post-treated by the method, and a polymer composite material including the treated carbonaceous material. More particularly, the present disclosure relates to a method for post-treatment of a carbonaceous material using dehydrocyclization, the method including subjecting the carbonaceous material to dehydrocyclization at room temperature to heal structural defects in the carbonaceous material obtained by a conventional method, while increasing the effective conjugated length of the carbonaceous material to improve the electrical conductivity thereof. The present disclosure also relates to a carbonaceous material post-treated by the method, and a polymer composite material including the treated carbonaceous material.
2. Description of the Related Art
Carbonaceous materials of nanomaterials have been used widely in various industrial fields by virtue of their excellent physical and chemical properties. Particularly, carbonaceous materials such as graphene, graphite, carbon nanotubes and fullerene have been spotlighted as materials for electric/electronic devices, optical devices and filter devices.
Graphene is one of the carbon allotrope materials including a sheet of carbon atoms formed by strong chemical covalent bonding between one carbon atom and another. Three electrons of the four valence electrons of a carbon atom forming graphene make sp2 bonding and form a strong covalent bond, i.e., sigma (σ) bond, while the remaining one electron not forming the bond makes π bonding with another carbon atom adjacent thereto. In this manner, the material itself forms a π-conjugated structure as a two-dimensional body having a hexagonal honeycomb lattice structure. Thus, graphene shows high electrical conductivity.
Recently, it has been most spotlighted to apply such excellent electrical conductivity of graphene to electric/electronic industries, or to production of highly conductive polymeric films including a polymeric resin filled with graphene as a conductive filler.
Graphene has an electron transportability approximately up to 15000 cm2/Vs at room temperature under ambient pressure, and in principle, shows a high electrical conductivity of 8×105 S/cm. However, in fact, graphene has a lower electrical conductivity than the calculated value.
Graphene is produced in the top-down approach and bottom-up approach. Production of graphene through the bottom-up approach is based on self-assembly of carbon atoms, and thus provides graphene having low defects. Therefore, the bottom-up approach is advantageous in that it provides high-quality graphene. However, production of graphene through the bottom-up approach is not amenable to mass production, and thus is limited in industrial applicability.
Mass production of graphene is essential to apply graphene to various industrial fields. To satisfy this, the top-down approach has been given many attentions. The top-down approach is based on separation or exfoliation of a graphite material by a chemical or physical process to obtain graphene or surface-modified graphene. The top-down approach is amenable to mass production and shows high cost efficiency, and thus has high industrial applicability. However, due to the chemical or physical treatment process, graphene obtained by the top-down approach has many defects, thereby providing a significant drop in electrical conductivity.
For example, when graphene is produced by oxidizing the surface of graphene chemically to increase the interlayer distance and to decrease the Van der Waals force between graphene sheets, and by applying force larger than the Van der Waals force thereto to perform exfoliation, it is required to remove the insulating oxygen functional groups formed on the surface in order to improve the electrical conductivity.
In general, hydrazine is frequently used to reduce graphene oxide. In this case, surface defects are formed while the surface functional groups are removed, and thus the resultant graphene shows low electrical conductivity so that it may not be used as a conductive filler.
Therefore, in order to apply such chemically oxidized/reduced graphene to various industrial fields, it is required that the surface defects formed during the reaction are decreased effectively to improve the electrical conductivity.
In addition, the same problems as mentioned above may be applied to the electrical conductivity and mechanical properties of carbon nanotube fibers. Since carbon nanotubes have excellent mechanical properties and electrical conductivity like graphene, they have been given many attentions in terms of their industrial applicability.
Currently, the most important industrial field, into which research and development of carbon nanotubes are conducted, is producing high-strength fibers including carbon nanotubes exclusively by agglomerating carbon nanotubes in the form of fibers. Since carbon nanotube fibers are those including carbon nanotubes exclusively, they have low specific gravity and are light, show excellent mechanical properties as well as high electrical conductivity. Thus, carbon nanotubes are materials to which many attentions are given in terms of their industrial applicability. However, like graphene, carbon nanotube fibers also have the problem of surface defects causing degradation of physical properties thereof.
Therefore, there has been a continuous need for developing a method for improving the electrical conductivity and mechanical strength of the resultant carbon nanotube fibers at the same time so that high-functional high-quality carbon nanotubes may be provided.